2.1 Earth's Crust in Motion

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Vocabulary

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earthquake- the shaking of plate tectonics
stress- the force that changes rock and its shape and volume
shearing- stress that pushes rock in opposite directions
tension- stress that pulls on rock making it thinner in the middle
compression- stress that squeezes rock until it breaks
deformation- the change in the Earth's crust such as its shape
Strike-Slip Fault- the rocks on both sides of the fault move past each other sideways
Normal Fault- in a normal fault,the fault is at an angle where one block of rock hangs above the fault and the other block lies beneath the fault
Hanging Wall- the block of rock that hangs above the fault is called the hanging wall
Footwall- the block of rock that lies beneath the fault is called the footwall
Reverse Fault- a reverse fault is the same as a normal fault, but instead of the block going underneath the other, in a reverse fault the blocks of rock move in opposite directions
Fault-block Mountain- these mountains form when a normal fault lifts a block of rock
folds- bends in rock that form when compression thickens part of the Earth's crust and shortens it
anticline- forms when a fold in rock bends upward
syncline- forms when a fold in rock bends downward forming a bowl
plateau- a large area of flat land that is higher than sea level

Outline

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Introduction

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• Everything in your house starts to shake and fall
  • After the shaking ends, you hear that an earthquake happened
    • Earthquakes are very destructive and they can destroy homes and object

Stress in the Crust

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• For years people have been thinking what earthquakes are
  • An earthquake is the shaking and trembling of plate tectonics
    • There are three types of stresses:shearing, tension, and compression

Shearing

• stress that pushes rock in opposite directions
  • can cause rock to break or change its shape

Tension

• stress that pulls on rock making it thinner in the middle
  • is like pulling on a warm piece of gum

Compression

• stress that squeezes rock until it folds or breaks
  • compressing rock is like a giant compactor

Kinds of Faults

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• there are three different types of faults
  • they are strike-slip faults, normal faults, and reverse faults.

Strike-Slip Faults

• make rocks on both sides to move past each other sideways.
  • form boundaries between plates.

Normal Faults

• during a normal fault the fault is at an angle where one block of rock lies above the fault and the other block lies beneath the fault.
  • the stress force tension creates normal faults in the places where plates diverge creating a divergent boundary

Reverse Faults

• a reverse fault is the same design as a normal fault but instead of the block going underneath the other,in a reverse fault the blocks of rock move in opposite directions
  • The stress force compression creates a reverse fault

Friction Along Faults

• the movement of rocks along a fault depends on the amount of friction there is between the opposite sides of the fault
  • a place along the fault where the friction is low and both sides of the fault go by each other without much stickyness
• place along the fault where the friction is normal, the sides of the fault collide together
  • a place along the fault where the friction is high, the rocks combine together and they stay
    • in some of these cases, the stress increases untill it's powerful enough to overcome the friction force

Mountain Building

• There are two ways by which mountains can form
  • They can by faulting and also by folding
• Mountains formed by faulting
  • Mountains formed by faulting are called fault-block mountains
    • These mountains form when a normal fault uplifts a block of rock
    • a example of a fault-block mountain range is the Sierra Nevada

Mountains formed by folding

• Mountains formed by folding are mountains that have formed when compression thickens part of the Earth's crust and shortens it as well.
  • An example of mountains formed by folding are the Himalayas and the Alps

Anticlines and Synclines

• anticlines form when a fold in rock bends upward forming an arch
  • anticlines are found in many places on the Earth's surface where the stress force compression have folded the surface
    • One example of an anticline are the Black Hills
• synclines form when a fold in rock bends downward forming a bowl.
  • synclines are also found in places on the Earth's surface where the stress force compression have folded the surface
    • One example of a syncline is the Illinois Basin

Plateaus

• a plateau is an area is a large area of flat land that is high above sea level
  • It has many flat layers and it is wider than tall
    • One example of a plateau is the " Four Corners " of Arizona, Utah, Colorado, and New Mexico.